A survey of hairy shaker disease (border disease, hypomyelinogenesis congenita) in sheep

A survey by mail in 1979 of 995 sheep farmers in Victoria enquiring as to the occurrence of hairy shaker disease (HSD) in lambs on their farms resulted in a 48% response. A total of 17 farms reported the presence of HSD. One hundred and eleven ewes produced lambs with HSD representing a small proportion only of the ewes (0.8%) on these farms and an even smaller percentage of the total ewes (0.03%) in the survey. Abortions were not prevalent on the majority of farms reporting HSD. There was no evidence that HSD was more common in any particular area in Victoria. As was anticipated mucosal disease virus/bovine virus diarrhoea (MDV) antibody was often present in serums from affected sheep. It was concluded that at present, the hairy shaker form of border disease did not appear to be an economically important problem in Victoria.     

A survey of ovine dermatophilosis in Western Australia

A random sample of 200 Merino sheep owners was interviewed by telephone during April 1983 and asked questions relating to the prevalence of ovine dermatophilosis in their flocks, methods used for prevention and treatment of dermatophilosis, management strategies employed and the location and annual rainfall of each farm. The response rate was 99.5%. During the previous 12 months 62.3% of farmers had observed dermatophilosis in their flocks. The prevalence within flocks was highest in hoggets (mean 2.2%, range 0 to 75%) followed by lambs (mean 0.8%, range 0 to 25%), ewes (mean 0.6%, range 0 to 20%) and wethers (0.2%, range 0 to 20%). The mean weight of wool identified as affected by dermatophilosis was 58 kg (range 0 to 882 kg). Preventive measures were used on 57% of farms and the most common methods were changes in dipping practice (23.6%) and culling of affected sheep (21%). An average of 13.7 sheep per farm were culled for dermatophilosis and of these, 82% were sold and the remainder (18%) were killed on the farm. Antibiotics, of which most were combinations of penicillin and streptomycin were used to treat dermatophilosis on 8.5% of farms and treatments other than antibiotics were used on 10% of farms. The prevalence of dermatophilosis and its relationship to various environmental and management factors varied with the age and sex of sheep. Discriminant analysis indicated that of the factors studied, average annual rainfall, month of lambing, average fibre diameter and the month ewes were shorn were related to the prevalence of dermatophilosis in lambs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemimelia and low marking percentage in a flock of Merino ewes and lambs

Hemimelia at a prevalence of 11% of lambs marked, and low marking percentage (51%) was observed in a flock of mixed age Merino ewes and their lambs. Hemimelia occurred in one or 2 limbs of affected lambs. Lambs from other flocks on the farm were unaffected, and the condition was not reported from other farms. The condition had not occurred in the past, and has not recurred. No infectious or hereditary factors were implicated in the aetiology of the condition. Grazing Western Australian Blue Lupin stubble by the affected flock during and after joining was the only known difference between this flock and others on the farm.     

A survey of excessively worn incisors and periodontal disease in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties

To determine the prevalence of excessively worn incisors (XSW) and periodontal disease (PD) in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties, the incisors of 4049 mixed age ewes on 83 farms selected at random were examined between December 1983 and February 1984. Of these ewes, 14.9% had XSW (11.7% moderate, 3.2% severe), 13.7% had PD (10.5% moderate, 3.2% severe) and 71.4% had sound mouths. An additional 43 ewes had miscellaneous incisor faults, and these were excluded from the survey. Seventeen (>20.5%) and 25 (>30.1%) farms had 20% ewes with XSW and PD respectively. On two farms only did XSW and PD each occur at a prevalence of 15%. No association was found between the prevalence of XSW or PD and body condition score, breed or farm topography.     

Resistance to macrocyclic lactone anthelmintics and associated risk factors on sheep farms in the lower North Island of New Zealand

AIM: To estimate the prevalence of resistance to macrocyclic lactone (ML) anthelmintics over a 3-year period on sheep farms in the Taihape area, and to determine associations between the presence of ML resistance and farm management practices. METHODS: All farmers with >1,000 lambing ewes served by one veterinary practice in the Taihape area of the central North Island of New Zealand were invited to take part in the study (n=157); respondents were selected on their willingness to participate. Resistance to ML was measured during 2004-2006, using a standard faecal egg count reduction test (FECRT) and a half dose of oral ivermectin (IVM; 0.1 mg/kg; n=84). Additional FECRTs were conducted separately on some farms, using full doses of IVM (n=47), levamisole (LEV; n=49), a benzimidazole (BZ; n=76), and a BZ/LEV combination (n=42). Resistance was defined as <95% faecal nematode egg count reduction (FECR) 7-10 days post-treatment. Larval cultures were performed on pooled faecal samples from all pre- and post-treatment groups for which any positive faecal nematode egg counts (FEC) were recorded. To ascertain whether particular management or drenching strategies were associated with the presence of resistance, a questionnaire comprising 50 questions was developed, and each farmer interviewed individually. RESULTS: Of all farmers invited, 84/157 (54%) participated in this study. Based on undifferentiated FEC, ML resistance to the half-dose IVM was evident on 46/84 (55%) participating farms. The majority of these cases (71%) involved Ostertagia (Teladorsagia) circumcincta. Resistance was also evident to full doses of IVM on 22/47 (47%), BZ on 41/76 (54%), LEV on 18/49 (37%), and BZ/LEV on 2/42 (5%) farms. Positive associations (p<0.05) were evident between the presence of ML resistance and management practices, such as: weaning over half of the lambs onto paddocks not grazed by lambing ewes since June; not always returning lambs to the same paddock after drenching; and the use of visual signs to assess 'worminess'. Measuring drench efficacy in January to March rather than later in the year, and presence of resistance to BZ or LEV were associated with a higher apparent prevalence of ML resistance (p<0.05). CONCLUSIONS: Anthelmintic resistance, and particularly ML resistance, was widespread on sheep farms in the Taihape area, and mostly involved O. circumcincta. The prevalence of resistance was lower on farms on which management practices, particularly those involving lambs, maintained refugia of unselected nematodes. Further investigation is required to develop control strategies which minimise selection for resistant worms, and how these may vary with climate.     

Methicillin resistant Staphylococcus aureus colonization in pigs and pig farmers

Methicillin resistant Staphylococcus aureus (MRSA) colonization has recently been identified in pigs and people that work with pigs, raising concerns about the role of pigs as reservoirs of MRSA for human infection. The objectives of this study were to evaluate the prevalence of MRSA colonization in pigs and pig farmers in Ontario, Canada and to characterize MRSA strains. Nasal and rectal swabs were collected from 285 pigs from three different age groups from 20 pig farms. Nasal swabs were collected from farm personnel and a brief questionnaire was also administered. The prevalence of MRSA colonization in farms was 45% (9/20) whereas the prevalence in pigs was 24.9% (71/285). There was no difference in MRSA colonization between age groups. The prevalence of MRSA colonization in pig farmers was 20% (5/25). There was a correlation between the presence of MRSA in pigs and humans on farms (P value=0.001). The results of spa typing revealed the predominant strain in pigs and humans was eGenomics spa type 539 (Ridom t034, clonal complex 398) which accounted for 59.2% of isolates and has been reported in pigs in Europe. A common human epidemic clone, CMRSA-2 (USA100, clonal complex 5) was also found in both pigs and pig personnel. Indistinguishable strains were found in pigs and pig personnel on all five farms with a colonized human. This study demonstrates that MRSA is common in pigs in Ontario, Canada, and provides further support to concerns about transmission of MRSA between pigs and humans.     

A survey of anthelmintic usage for sheep: a time for change

A sample survey of anthelmintic usage and farmers; drenching policies was conducted on 614 sheep farms, in the North and South Islands, selected from among those carrying 1500 or more breeding ewes. The survey was based on information for the 1978179 and 1979/80 farming years recorded on questionnaires completed during personal interviews between Livestock Officers and the farmers concerned. Results show that there were no significant between-Island differences in mean drenching frequencies for any age class of sheep. In 1979/80, the overall New Zealand drenching frequencies were 6.3 for lambs, 1.8 for 1-2-year-olds and 1.2 for sheep older than 2 years. Of the farmers surveyed, 20% did not drench 1-2-year-old sheep and 29% did not drench sheep older than 2 years. There were also no between-Island differences in timing of drenches and alternation of drench brands. Sixty-nine per cent of the farmers followed a pre-determined drenching programme whereas 27% stated that they drenched if and when necessary. For lambs, some drenching was carried out in all months of the year hut fewer farmers drenched during the mid-winter to mid-spring period (July-October). Older stock were drenched in all months also but there was a general acceptance by farmers of the practices of pre-tupping and pre or post-lambing drenching. At the time of the survey, 48% of the farmers were using three or more brands of drench with a maximum of nine. Analysis of data relating to brands of drench used shows that whereas 39% of the farmers w,ere alternating drench families [i.e. benzimidazoles (BZ) c.f. non-benzimidazoles (NBZ)] within a single farming year, only 3% were practising a strict alternation of drench families between years. General comments by the farmers surveyed indicate a disturbing degree of misunderstanding and misconception regarding the properties and limitations of current anthelmintics. The survey also revealed a lack of appreciation of the rationale of prophylactic (;preventive;) parasite control. These aspects are discussed in relation to currently recommended control strategies and the problem of anthelmintic resistance.     

The geographic distribution of carcinomas of the small intestine in New Zealand sheep

A sample survey of anthelmintic usage and farmers' drenching policies was conducted on 614 sheep farms, in the North and South Islands, selected from among those carrying 1500 or more breeding ewes. The survey was based on information for the 1978/79 and 1979/80 farming years recorded on questionnaires completed during personal interviews between Livestock Officers and the farmers concerned.

Results show that there were no significant between-Island differences in mean drenching frequencies for any age class of sheep. In 1979/80, the overall New Zealand drenching frequencies were 6.3 for lambs, 1.8 for 1-2-year-olds and 1.2 for sheep older than 2 years. Of the farmers surveyed, 20% did not drench 1-2-year-old sheep and 29% did not drench sheep older than 2 years.

There were also no between-Island differences in timing of drenches and alternation of drench brands. Sixty-nine per cent of the farmers followed a pre-determined drenching programme whereas 27% stated that they drenched if and when necessary. For lambs, some drenching was carried out in all months of the year but fewer farmers drenched during the mid-winter to mid-spring period (July-October). Older stock were drenched in all months also but there was a general acceptance by farmers of the practices of pre-tupping and pre- or post-lambing drenching.

At the time of the survey, 48% of the farmers were using three or more brands of drench with a maximum of nine. Analysis of data relating to brands of drench used shows that whereas 39% of the farmers were alternating drench families [i.e. benzimidazoles (BZ) c.f. non-benzimidazoles (NBZ)] within a single farming year, only 3% were practising a strict alternation of drench families between years.

General comments by the farmers surveyed indicate a disturbing degree of misunderstanding and misconception regarding the properties and limitations of current anthelmintics. The survey also revealed a lack of appreciation of the rationale of prophylactic (‘preventive’) parasite control. These aspects are discussed in relation to currently recommended control strategies and the problem of anthelmintic resistance.     

Salmonella Brandenburg: case-control survey in sheep in New Zealand

AIM: To identify environmental, management and animal risk factors associated with the occurrence and severity of disease attributed to Salmonella Brandenburg infection in sheep. METHODS: A retrospective case-control study was undertaken, and details of disease prevalence and farm management methods were collected from two affected regions in southern New Zealand. Associations between possible risk factors and disease attributed to S. Brandenburg were evaluated using odds ratios. A case-control approach was used to assess risk factors associated with outbreaks of disease at the farm level, using unaffected farms as controls. A separate analysis was then performed within affected farms only, to assess risk factors associated with increasing severity of disease. RESULTS: Data were collected from 405 farms containing a total of 1,170,737 ewes. Of the 177 case farms, 172 (97%) had diseased mixed-age ewes, 78 (45%) had diseased two-tooth ewes and eight (5%) had diseased hoggets. Increased odds of farms being affected with S. Brandenburg were reported for farms that strip-grazed sheep, and as total numbers of sheep increased. Reduced odds of being affected were associated with feeding crops, and hilly terrain on those farms not feeding crops. Within affected farms, increased severity of disease was associated with strip-grazing and feeding hay in TT flocks, and later removal of rams in MA flocks. Reduced severity of disease was associated with shearing or crutching after July, and vaccination of sheep against Salmonella spp. CONCLUSIONS: Salmonella Brandenburg occurred in flocks that reported using intensive farming methods and that maintained high numbers of sheep. CLINICAL RELEVANCE: Risk factors associated with the occurrence and severity of the disease due to S. Brandenburg have been identified. This information is necessary to identify preventative and control measures that may be effective in reducing the risk of disease.     

Slaughter findings feedback systems--its use for farms of origin?

Over a period of 22 months 13 official meat inspection authorities examined a number of 152 520 swine at an Austrian slaughterhouse for pathologic-anatomic changes (five parameters). Of those veterinarians whose reliability in the recording of findings was a given, the results were analysed by employing a mathematical model which assessed whether the activities of 25 attending veterinarians and 223 farmers actually lead to an improvement of animal health in their livestock. Mild pneumonia was registered in 14.5% of swine; no attending veterinarians had any influence whatsoever on the occurrence of this parameter. Farmers' activities improved animal health on two farms (0.9%), six farms of origin (2.69%) showed significantly lower findings than the average of all farms. Pleurisy was ascertained in 22% of all slaughter pigs. Through measures taken, four attending veterinarians (16%) caused a reduction of incidents, two works managers (0.9%) made worse, six farmers (2.69%) improved animal health of their live stock. Seven farmers (3.14%) showed significantly (p < 0.05) higher, 28 farms (12.6%) lower prevalence. Pericarditis affected 4.5% of the animals in question. On all farms of origin the condition of health remained unchanged by measures taken by veterinarians. On two farms (0.9%) the influence exercised by farmers led to a deterioration of the health of swine, six businesses (2.69%) showed higher, one (0.45%) lower prevalence than on average. 6.2% of swine showed white spots. Attending veterinarians did not influence this parameter at all. With preventive measures taken five farms (2.24%) showed less, three farms (1.35%) higher prevalence by the end of the 22 month term. Mange concerned 2.2% of all slaughter pigs. The activities of one veterinarian (4%) caused the number of incidents to double; on six farms (2.69%) a significantly higher prevalence was registered. Whatever influence exercised, the status of health of slaughter pigs remained unchanged throughout the duration of the study.     

The epidemiology of squamous cell carcinoma of the perineal region of sheep: Abattoir and flock studies

The roles of age, tail length and the Mules operation in the epidemiology of squamous cell carcinoma in ewes were studied. The prevalence of the disease in adult sheep slaughtered at 2 abattoirs was 0.08%. No cases occurred in lambs. Of all adult sheep condemnations before slaughter, 38.5% were due to squamous cell carcinoma. Of these sheep, 73.3% had a single lesion of the vulva (62.9%), tail (6.6%), or anus (3.8%), while 26.7% had lesions at more than one site. The number of lesions was significantly greater (p < 0.01) in sheep with a radical Mules operation than in those with a modified Mules operation or not mulesed. Tails were significantly shorter (p < 0.01) in affected than unaffected sheep. Small keratinised outgrowths on the skin of the tail and perineum were considered on histological grounds to be precursors of squamous cell carcinomas. On one affected farm 4% of ewes were culled in one year for gross lesions of squamous cell carcinomas. A further 3.5% of sheep with gross lesions and 25.3% with precursor lesions remained in the flock, undetected by the farmer. Gross lesions were not observed in ewes under 3 years of age, whereas precursors occurred in all age groups, including one-year-old ewes. The prevalence of lesions increased with age, from 0.43% in 5-year-old ewes to 5.14% in 6-year-old and 41% in 7-year-old ewes. Discriminant analysis indicated that age of ewe, tail length and the width of the healed Mules operation were important determinants of squamous cell carcinoma. In all the sheep studied the style of mulesing was consistently radical, with a mean healed width of 12.3 ± 2.6 cm. Tails were amputated much shorter than the traditionally recommended length of level with the tip of the vulva. The presence of gross and precursor lesions was associated with shorter tails and a radical Mules operation. It is suggested that the prevalence of the disease may be reduced by the adoption of a less severe mulesing technique and leaving tails longer.     

The seroprevalence of maedi-visna in Ontario sheep flocks and its relationship to flock demographics and management practices.

The objectives of this study were to describe the serological prevalence of maedi-visna in a sample of Ontario sheep flocks, and to identify management and demographic variables that were associated with seroprevalence for maedi-visna. A sample of 103 sheep flocks in Ontario was randomly selected from those flocks participating in the Red Meat Plan. The owners of these flocks were surveyed regarding management procedures on their farms, and blood samples were taken from a random sample of ewes in each flock. At least one ewe tested serologically positive, based on the agar gel immuno-diffusion test, in 69.9% of the farms. Positive serological reactions occurred in 20.9% of the 3880 sheep tested. Flock demographics and farm management variables were considered in a multiple regression model, and several factors were positively associated with higher maedi-visna seroprevalence rates. These included the average age of the flock, the number of years the owner had been sheep farming, the practice of using foster ewes, the practice of allowing lambs to have contact with other ewes that are lambing, and the average pasture acreage per ewe.     

Akabane disease in sheep

Perinatal lamb mortality, associated with malformations of the CNS due to Akabane viral infection, occurred in 4 of 9 flocks of ewes lambing on 3 farms between 26 May and 14 November, 1976. Cases were restricted to ewes conceiving prior to the second week of March and lambing between 26 May and 19 July. As judged by seroconversion in sentinel flocks on 2 of the farms, field infection with Akabane virus occurred mainly between mid-February and mid-April. Malformations of the CNS occurred in 42.5%, 51.2%, 100% and 31.0% of the dead lambs examined in the affected flocks respectively. Prevalence in the 4 affected flocks, expressed as the proportion of ewes lambing which delivered at least one malformed foetus, was 6.1%, 8.4%, 88.9% and 5.7% respectively. Lamb mortality due to malformations of the CNS was 7.1%, 5.5%, 92.3% and 5.7% of lambs born. Age-specific prevalence was calculated for 3 of the 4 flocks and 2-year-old ewes accounted for 71.4% and 76.9% of total cases respectively in 2 flocks, whereas in one flock malformations occurred at equivalent frequencies throughout several older age groups. Birthweights of affected lambs were usually significantly lighter than those of unaffected lambs of similar sex and birth-type, and their mean duration of gestation was slightly, and significantly, prolonged. Micrencephaly (88.1% of cases) and hydrocephalus (68.7% of cases) were the outstanding pathological features of the malformations with hydranencephaly, microgyria, porencephaly and attenuation of the spinal cord occurring at much lower frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)     

A field study of the association between periodontal disease and body condition in sheep

Three farms with a high prevalence of periodontal disease (PD) were selected using data from a December 1983/January 1984 survey. On each of these farms in August 1984, the incisor condition and body condition score of about 50 ewes were noted. Two of the farms and an additional farm with a high prevalence of PD were visited again in August 1985, and on each, incisor condition and body weights of about 150 ewes were recorded. On one farm only was there a significant association between PD and body condition or weight, and it occurred in both years.     

Glutathione peroxidase (GPX) activity in blood of ewes on farms in different scrapie categories in Iceland

Background

Preliminary studies indicated decreased glutathione peroxidase (GPX) activity in blood of ewes on scrapie-afflicted farms. Other studies have shown decreased GPX activity in brain of prion-infected mice and in prion-infected cells in vitro. The aim of this study was to examine the GPX activity in blood as well as the distribution of GPX-activity levels from ewes on farms in scrapie-afflicted areas in Iceland.

Methods

Blood samples were collected from 635 ewes (non-pregnant [n = 297] and pregnant [n = 338]) on 40 farms in scrapie-afflicted areas during the years 2001–2005, for analysis of GPX activity. The farms were divided into three categories: 1. Scrapie-free farms (n = 14); 2. Scrapie-prone farms (earlier scrapie-afflicted, restocked farms) (n = 12); 3. Scrapie-afflicted farms (n = 14). For comparison, 121 blood samples were also collected from non-pregnant ewes on one farm (farm A) in a scrapie-free area (scrapie never registered). Chi-square test was used to test for normal distribution of GPX-results, and Kruskal-Wallis test to compare GPX-results between categories.

Results

The GPX-results appeared to be biphasically distributed in ewes in all three scrapie categories and on farm A. The presumptive breaking point was about 300 units g Hb^-1. About 30–50% of the GPX-results from ewes in all three scrapie categories were below 300 units g Hb^-1 but only about 13% of the GPX-results from ewes on farm A. The mean GPX activity was highest on farm A, and was significantly lower on scrapie-prone farms than on scrapie-free or scrapie-afflicted farms (non-pregnant and pregnant ewes: P < 0.005, respectively; non-pregnant and pregnant ewes combined: P < 0.0005).

Conclusions

1) the distribution of GPX-results in blood of Icelandic ewes apparently has a biphasic character; 2) the GPX-results were higher in ewes on one farm in a scrapie-free area than in ewes on farms in the scrapie-afflicted areas; 3) GPX-activity levels were significantly lowest on earlier scrapie-afflicted, restocked farms, which might have a bearing on the recurrence of sporadic scrapie on these farms; 4) further study on the possible role of GPX activity in the occurrence of scrapie in Iceland is warranted.     

A field study of the association between periodontal disease and body condition in sheep

Three farms with a high prevalence of periodontal disease (PD) were selected using data from a December 1983/January 1984 survey. On each of these farms in August 1984, the incisor condition and body condition score of about 50 ewes were noted. Two of the farms and an additional farm with a high prevalence of PD were visited again in August 1985, and on each, incisor condition and body weights of about 150 ewes were recorded.

On one farm only was there a significant association between PD and body condition or weight, and it occurred in both years.     

A survey of helminth control practices on sheep farms in Great Britain and Ireland

A telephone survey of 600 farmers throughout Great Britain and Ireland was conducted in order to characterise helminth control practices, and identify factors correlated with perceived anthelmintic failure. Overall, 93% of surveyed farmers routinely treated their sheep against nematodes, 67% against liver fluke and 58% against tapeworms. Anthelmintic resistance in nematodes was perceived by farmers to be present on 10% of farms. Farmers who dosed ewes at mating were more likely to have observed anthelmintic failure, than those who were aware of national guidelines on parasite control. However, objective assessment of anthelmintic efficacy had only been undertaken on 19% of farms. Ewes were treated at mating and lambing on 63% and 62% of farms, respectively. On average, lambs were treated 3.6 times annually, depending on geographical region and on dates of lambing and finishing. Although 'quarantine' treatments were widely administered to bought-in stock, these were appropriately applied in only 3% of cases. This study provides baseline data against which the impact of future anthelmintic information campaigns can be assessed; it will facilitate the development of rational, farm-level mathematical models in support of sustainable parasite control, and will aid in the design of farm management practices that prolong the effective lifespan of novel classes of anthelmintic.     

Myiasis in sheep in The Netherlands

In 1999, among 164 randomly selected Dutch sheep farmers, a questionnaire was carried out to estimate the prevalence of myiasis in sheep and to investigate factors associated with the occurrence of myiasis. The total number of sheep and/or lambs on the reference date 1 August 1999 was 12,200: 5243 ewes, 225 rams, 3393 ewe- and 3339 ram lambs. On 86 (52.4%) of the farms 349 (2.9%) of all sheep and/or lambs contracted myiasis, of which two died. Myiasis was seen significantly more frequently on farms with over 25 ewes compared to smaller farms. Cases of myiasis were detected from April to September, with a peak (47.1%) in August. Occurrence of myiasis was most frequently associated with hot and humid weather and was mainly observed (69.1%) in the area around the tail.Ewes and ewe lambs had significantly more myiasis when compared with rams and ram lambs. There was no relationship with tail docking, with breed, with the time of shearing, with the kind of soil (clay, sand, etc.), with the environment (bush, trees, water, etc.), with the type of treatment (pour on, dipping, spraying), the used insecticides (synthetic pyrethro?ds, diazinon, cyromazin, etc.), the number of preventive treatments, the time of treatment or the number of observations on the herd (once a day, once a week, etc.).     

Nutritional factors associated with vaginal prolapse in ewes

Serum calcium, magnesium and phosphate values of ewes recently affected by vaginal prolapse were compared with unaffected ewes in four flocks. Subclinical hypocalcaemia was demonstrated in some affected and unaffected ewes in three flocks. Magnesium and phosphate values were normal. In two flocks the body condition of ewes recently affected by vaginal prolapse was variable and reflected the variation in condition found in the flock. In a third flock affected ewes had significantly lower body condition scores than unaffected ewes (P less than 0.001). Analysis of the fourth flock was not possible. Oestrogenic mycotoxins were not detected in any of the feed samples taken from these flocks. The following year the management, nutrition and energy, and the protein and calcium status of ewes in 12 flocks of greyface/mule ewes with a history of a regular high (greater than 3 per cent) or low (less than 1 per cent) prevalence of vaginal prolapse were compared. A high prevalence was not associated with any particular feedstuff. A high or intermediate (1 to 3 per cent) prevalence of vaginal prolapse was found in three of the four flocks managed as a single group and these three flocks were fed on an unrestricted basis. Body condition scoring and beta-hydroxybutyrate estimation confirmed that ewes in these flocks were overfed. The prevalence of vaginal prolapse in the flocks was not related to the serum albumin, calcium or urea of the ewes. Therefore subclinical hypocalcaemia was probably a consequence of vaginal prolapse rather than a cause.     

THE INCIDENCE OF DYSTOCIA IN DORSET HORN EWES

The incidence of dystocia was recorded in flocks of Dorset Horn ewes lambing in winter, spring or summer and grazed at 8, 12 or 16 ewes per hectare over a ten-year period. The mean incidence of dystocia was 34% of ewes lambing. Significantly more ewes experience a difficult birth at winter (35%) and spring (39%) than summer (26%) lambings. Neither stocking rates nor pre-lambing ewe bodyweight were related to the incidence of dystocia. The incidence of dystocia was significantly greater in 2-year-old ewes than in any other age group. Foetal size was of major importance in the occurrence of dystocia. Approximately 60% of single and twin born lambs that had birth weights greater than 4.5 kg had a difficult birth whereas in lambs weighing less than 3.2 kg only about 10% were affected. Thirty-six per cent of all perinatal mortality was attributable to dystocia. Approximately 27% of single and 73% of twin presentations in assisted births were abnormal, 31% of all lambs assisted had 1 or both legs retained, 4% had posterior (including breech) presentations and the remaining 8% were of varied forms of malpresentation. Significantly more single male than female lambs experienced a difficult birth and the mean birth weights of single, twin and triplet born lambs that had a difficult birth were greater than the birth weights of singles, twins and triplets born normally.